1. Field of Invention
This invention relates generally to pellet stoves, specifically to a portable pellet stove with improved air flow and insulation.
2. Prior Art
Pellet stoves are combustion devices that bum small pellets of wood-based fuel with very high heat content; the heat generated is typically used for space heating or cooking.
Our U.S. Pat. No. 5,123,360 (1992); as well as U.S. Pat. No. 4,619,209 to Traeger et al. (1986); U.S. Pat. No. 4,565,184 to Collins et al. (1986); and U.S. Pat. No. 3,223,077 to Tsakos (1965), show pellet stoves with a storage bin for holding a supply of fuel pellets, and a motor-driven auger or screw conveyer for feeding the pellets at a predetermined rate into a firepot or burner for combustion.
In the Collins, Tsakos, and Traeger devices, a horizontal pellet conveyer terminates at the base of the firepot, so that the distal end of the conveyer is in contact with the combustion zone. Therefore these stoves require long distances between the combustion zone and heat sensitive components, such as the fuel bin and feed motor, for safe thermal separation, and long feed conduits to connect them. As a result, these stoves are too large to be truly portable. These stoves also show air blowers for supplying fresh air through the combustion area. However, the air is directed across the top or the sides of the fuel pile in the firepot, so that the lower or inner areas of the fuel pile therein will not receive enough air for efficient combustion. In the Collins device, the bottom of the fuel bin is separated from the hot combustion area by a single-layered wall, so that the stored fuel may get dangerously hot. Furthermore, the air blower that exhausts the hot gases is subjected to very high temperatures, so that its reliability may also be reduced.
Our patent shows a blower for directing air through the firepot from a perforated bottom thereof for efficient combustion. The screw conveyer is separated from the firepot by a short chute, so that it is not in direct contact with the burning fuel. The conveyer is also kept cool by forced-air flowing from the chute. Although the air flowing through the chute follows a contorted path through the small spaces between the fuel pellets in the storage bin and the screw conveyer, the speed of the flow may be high enough for sufficient cooling when the fuel is in such close proximity to the combustion zone. However, the stove has only a single-layered barrier between the firepot and the compartment housing the electrical components, which may not be sufficiently insulated from the heat, in some cases.
These and all other prior-art pellet stoves either have conveyers that are exposed directly to the burning fuel, or do not provide enough air flow to the fuel pellets for efficient combustion, in some cases. Additionally, some do not sufficiently insulate the electrical components from the heat of combustion, some require such long spatial separations between the combustion zone and the other components so as to make the stoves too large to be portable, some have firepots that are permanently mounted and cannot be removed for cleaning, and some use long feed conduits that make the stoves too large to be truly portable.